Reproductive Genetics 3 Flashcards
Describe the risks for aneuplodiy or single gene disorders for patients based on age, prior history, or screening results.
1
Q
What is confined placental mosaicism?
A
- Found in approximately 1% of CVS samples
- Confirmed in fetus in 23% of cases
- Amniocentesis often recommended
- CPM may be associated with IUGR
- Trisomy 17 will always indicate CPM
2
Q
What is spinal muscular atrophy (SMA)?
A
- Autosomal recessive progressive neurodegenerative disorder
- lower motor neurons in anterior horn of spinal cord
- Symmetric proximal msucle weakness
- progresses to hypotonia and respiratory failure at age 2
- Most common form of a result of homozygous absence of functional SMN1 gene
- Incidence is 1 in 6000
3
Q
Describe the risks of osme of the common aneuploidies in liveborn babies.
A
- Trisomy 21 (Down syndrome) - 1 in 700
- Trisomy 18 (Edward syndrome) - 1 in 3000
- Trisomy 13 (Patau syndrome) - 1 in 5000
- 45, X (Turner syndrome) - 1 in 2500 females and 600 males
- 47,XXY (Klinefelter syndrome) - similar to Turner
- 47, XYY and 47, XXX - 1 in 1500
4
Q
What fetal chromosome abnormality does not increase with maternal age?
A
Polyploidies or microdeletions
5
Q
What is the risk for recurrence in aneuploidy?
A
- If women have miscarriages that are due to chromosome abnormality the first time around, the second one will have an increased risk of aneuploidy
- Risk is much lower for someone who is a carrier, not 33%
- most aneuploidy pregnancies spontaneously miscarry
- Risk is much higher if the mother is the carrier of the translocation versus the father
- sperm carrying extra chromosomes aren’t as able to fertilize the eggs